Apex domains cannot have CNAME records.
Question and response
Question
dig asahi-net.or.jp. NS
Answer
asahi-net.or.jp. 5 NS crusader.asahi-net.or.jp.
asahi-net.or.jp. 5 NS dns1.asahi-net.or.jp.
Authority
The response has no authority records.
Additional
dns1.asahi-net.or.jp. 5 A 202.224.39.149
crusader.asahi-net.or.jp. 5 A 202.224.39.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0